Recent conceptualizations of attention deficit hyperactivity disorder (ADHD) have emphasized its chronicity and refractoriness. Despite numerous studies that have examined the short-term efficacies of psychostimulant medication, psychosocial treatments such as behavior modification, and combined pharmacological and behavioral treatments, it is clear (a) that all of these treatments lack sufficiency in the short-term and (b) that no intervention has documented long-term effectiveness. As a result, there is no clear answer to the question, "What constitutes the best treatment for ADHD?" There are widely disparate answers to this question within the professional community, with some arguing strongly for the efficacy and sufficiency of pharmacological interventions, while others argue just as strongly for the primacy of psychosocial treatments, and still others believe that combined interventions will prove most efficacious. The purpose of the proposed study is to address some of the unanswered questions regarding the best treatment for ADHD by evaluating the separate and combined efficacies of several different treatments for ADHD children. Thus, eighty ADHD children will be recruited to participate in a three-year study in which they will be assigned to one of three psychosocial treatment groups: (1) Maximum intensity treatment consisting of parent training, intervention within the children's home school settings, and intervention for peer relationships and academic deficits provided through intensive summer treatment (STP) and Saturday treatment (SaTP) programs; (2) intensive outpatient treatment consisting of the same parent training and intervention within the children's home school settings provided to the maximum intensity group; and (3) a contact control group. After four months of treatment, all children will participate in a double-blind, placebo-controlled, within-subject medication assessment conducted in their school and home settings. Based on this assessment, children who are positive responders to medication within each psychosocial treatment group will be assigned to one of three medication groups, with medication to continue concurrently with continued psychosocial treatment: (a) best dose CNS stimulant t.i.d. 7 days per week; (b) best dose CNS stimulant b.i.d. on school days only (with placebo necessary to match pill regimen of the first group); and (c) placebo t.i.d. 7 days per week. Concurrent psychosocial and pharmacological treatment will continue for two years. At the end of this period, medication will be withdrawn from half of the children. Periodic assessments will evaluate the child's functioning in the family, classroom, and peer domains. The major questions addressed involve the relative efficacies of the separate and combined treatments and whether treatment efficacy interacts with domain of functioning and individual difference variables that include age, gender, severity of impairment, comorbid child diagnoses, self-perceptions of competence, attributional style, parental psychopathology, family SES, and parental marital status.